1. Field of the Invention
The present invention relates to a manufacturing method of a timepiece part and the timepiece part.
2. Description of the Related Art
As material of a timepiece part, titanium or titanium alloy (hereinafter, referred to as “titanium or the like”) which is lightweight is widely used. By anodizing processing with respect to the timepiece part formed of the titanium or the like after the shape processing, corrosion resistance can be provided. In addition, by adjusting the condition of the anodizing process, various hues can be provided.
In general, it is difficult to provide a metallic luster in the anodizing process with respect to titanium or the like. Thereby, there is a problem in that a timepiece part lacks the high grade sense.
In JP-A-11-100627 (Patent Reference 1), the following technology is described as a manufacturing method of a titanium product or a titanium alloy product. That is, the material of titanium or titanium alloy is heated in a vacuum or an inert gas at a temperature of 900 to 1500° C., and crystal grains including twin crystals of 100 μm or more are precipitated on a portion or the entirety of the surface or the end. In the titanium or the titanium alloy product which is manufactured by the above method, a crystal surface is aligned in slightly different directions with respect to the normal direction of a metal surface, and it is considered that the crystal surface shines brilliantly according to the viewing angle.
However, in order to obtain a sufficient metallic luster in Patent Reference 1, it is necessary to secure a light reflection area of the crystal surface by coarsening the crystal grains to several mm or more in reality. If the invention of Patent Reference 1 is applied to a timepiece part which is a minute part and the crystal grains are coarsened more than the timepiece part, there is a probability that the timepiece part is formed of one grain (is constituted by a monocrystal). In general, since the hardness of polycrystalline material of the titanium or the like is different for each crystal, if the timepiece part is formed for each crystal, the hardness of the timepiece part varies.